1. Field of the Invention:
This invention relates to a V belt which is mainly used for high load transmitting in a dry type transmission. The V belt according to the present invention is usable not only as the V belt of a continuously variable transmission for motor vehicles but also as the V belt of a continuously variable or uncontinuously variable transmission for vehicles loaded with an engine, such as agricultural machines and civil engineering machines. Also, it is most suitable for the V belt for high load of general industrial machines to be driven by electric motors. Furthermore, it can be used as a belt for transportation or printing by utilizing the upper surface of its block.
2. Background of the Art:
Generally, the V belt for motor vehicles is required to have ability to transmit very high torque, for example, when the maximum torque of 1,000 cc engine is transmitted by a rubber V belt, the V belt must stand the lateral pressure of around 20 Kg/ cm.sup.2. However, typical rubber V belts in practical use at present are usually used under the condition of less than 4-5 Kg/cm.sup.2 and even rubber V belts for high load cannot be used under the condition of more than 10 Kg/cm.sup.2.
As the V belt which meets the requirement mentioned above, the applicants previously developed and suggested such a V belt which is composed by fitting a plurality of blocks to a pair of endless load carriers by engagement of a concaved part with a convexed part, as disclosed by the Japanese Patent Application Laying Open No. 60-49,151 (corresponding to U.S. patent application Ser. No. 634,885 now U.S. Pat. No. 4,655,732).
Further studies of the applicants in this field for improving flexuosity and for application to the pulley of small diameter led them to conceive the idea of a new V belt with load carriers having cogs at their underside and blocks having at their slot under surface curved convexed surfaces, with which valleys between adjoining cogs are engaged. Such V belts, however, raised the problem that if the cog top is extending downwardly beyond the slot under surface of the block, the lower end of the cog top is compressed and deformed to a large extent at the front and rear surfaces of the block when the belt was wound round pulleys and as a reaction of it, force applied to the block becomes excessively large, with the result of earlier breakage of the block.
In the above-described V belt, since load carriers and blocks are engaged with each other only by engagement of a concaved part and a convexed part, fixing of blocks to load carriers is not firm and this causes such troubles as melting and degradation of the block due to frictional heat generates by surface pressure and slip between the load carrier and the block, breakage of the block due to reduced strength caused by high temperatures, cracks in load carriers due to hardening of rubber material and so forth, all of which relate to the shorter service life of the belt.
The applicants developed further such a V belt which has high flexuosity and applicability to a pulley of small diameter by engagement of the block and the load carrier with each other in such a fashion that the slot under surface of the block and the under surface of the load carrier correspond to each other with the least pulley diameter (for example, refer to the Japanese Utility Model Registration Application Laying Open No. 60-173746). However, since the pulley pitch diameter varies during running of the pulley, there exists the so-called "play" between the block and the load carrier in the case of the pulley diameter which is larger than the minimum pulley diameter, especially in high speed running, frictional heat generated at the engaging part is large, with the result of shorter service life of the belt.